1. Field of the Invention
The present invention relates to an optical beam scanning apparatus for scanning a recording medium with a beam of light in an optical recording and reproducing apparatus, such as an optical disk apparatus using a hologram.
2. Description of the Related Art
In a conventional optical beam scanning apparatus, a recording medium such as a rotational optical disk is scanned with a beam which is converged onto a predetermined position of the optical disk, for example, by rotation of the optical disk or radial linear movement of an optical pick-up. In this apparatus, however, a problem of deviation of a scanning beam arises because of surface fluctuations (oscillation) due to the rotation of the optical disk or a possible eccentricity of the center of the rotation. Nevertheless, this problem can be solved by the servo-drive of the optical pick-up.
Such a servo-drive, however, and the necessary precise control of the rotational and linear movements of the optical disk and the optical pick-up, make the apparatus more complicated and more expensive. Furthermore, the conventional scanning apparatus has a low scanning speed, and less resistance to noise and oscillation, and further, there is only a small freedom of posture of use of the apparatus.
The primary object of the present invention is to provide an optical beam scanning apparatus by which a beam of light can be converged onto a desired position of an optical recording medium, such as an optical disk, without moving an optical pick-up or the optical recording medium.